One thing... Could do the same whith outer cirle and black? Hi, Jabier.

El dom, 16-06-2013 a las 00:17 +0530, Arshdeep Singh escribió:

Okay guys, no need for the above said approaches, I took care of it using saturation adjustment itself. :) Here's a snapshot: Inline image 1

On Sat, Jun 15, 2013 at 11:10 PM, Arshdeep Singh <moduli16@...400...> wrote: Hello devs, My current state of the wheel looks like this: Inline image 1

    I want a white center that blends into the respective colors
    towards the circumference.
    Here's a snippet from gimpcolorwheel.c
    Function : static void paint_ring (GimpColorWheel *wheel,
    cairo_t *cr) { ...}

    Snippet:
    for (yy = 0; yy < height; yy++)
        {
          p = buf + yy * width;
          dy = -(yy - center_y);


          for (xx = 0; xx < width; xx++)
            {
              dx = xx - center_x;


              dist = dx * dx + dy * dy;
              if (dist < ((inner-1) * (inner-1)) || dist > ((outer
    +1) * (outer+1)))
                {
                  *p++ = 0;
                  continue;
                }


              angle = atan2 (dy, dx);
              if (angle < 0.0)
                angle += 2.0 * G_PI;


              hue = angle / (2.0 * G_PI);


              r = hue;
              g = 1.0;
              b = 1.0;
              hsv_to_rgb (&r, &g, &b);


              *p++ = (((int)floor (r * 255 + 0.5) << 16) |
                      ((int)floor (g * 255 + 0.5) << 8) |
                      (int)floor (b * 255 + 0.5));
            }
        }


    this paints the colors of the wheel. Because we need to paint
    the center white, we have two options: ( I suppose ? )
    One is to include a distance from the center that shall be the
    faintest white from the center  We can choose this distance to
    be 20% of the radius allocated. This white coloration can
    be accommodated into the above snippet but what I fail to
    solve is how to add the transparency ? Should I calculate a
    separate 'buf' that is then OR-ed (overlaid) with the 'p'
    buffer to create that effect ?

    OR

    I can create a smaller circular arc and use radial gradient
    (white at center and transparent at circumference , radius
    again 20% ) and overlay onto the same surface used to draw the
    initial color wheel as shown in the picture above. 

    I personally feel, the second option is easier because the
    first option would require to know how rgb changes when a
    certain degree of white is added to it. Your views are looked
    forward to. 
    Thanks.


    -- 
    Arshdeep Singh
    Third Year, Computer Engineering
    Delhi Technological University
    Ph: +91-9654115614
    https://sites.google.com/site/adsingh1729/home

-- Arshdeep Singh Third Year, Computer Engineering Delhi Technological University Ph: +91-9654115614 https://sites.google.com/site/adsingh1729/home

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